1. Field of the Invention
The present invention relates to an environmental gas sensor and a method of manufacturing the same, and more particularly, to an environmental gas sensor which can simultaneously measure two kinds of gases through a sensing layer on which different kinds of nanofibers are arranged perpendicular to each other.
2. Discussion of Related Art
In recent times, growing concerns about environmental pollution and health have increased the necessity to sense various environmentally-harmful gases. The demand for a harmful gas sensor which has developed in response to the demand to sense toxic and explosive gases is growing to increase the quality of human life through, for example, health care, monitoring of living environment, industrial health and safety, home appliances and home automation, food and agriculture, manufacturing processes, and national defense and terror.
Thus, the gas sensor will become a means for building a disaster-free future society, and must adapt to more precisely measure and control environmentally-harmful gases.
Since new services such as a ubiquitous sensor system and an environmental sensing system are being realized, such a sensor system should satisfy several conditions in order to be commercialized. First, the gas sensor should have high sensitivity so that it can detect a low-concentration gas. Second, the gas sensor should have selectivity so that it can selectively sense a specific gas without influencing a co-existing gas. Third, the gas sensor should have stability, so that it does not influence surrounding ambient temperature and humidity and stably senses a gas, and should not be degraded according to time. Fourth, the gas sensor should have fast response speed, so that it can rapidly and repeatedly react with gases. Fifth, the gas sensor should have multi-functionality and low power consumption. To meet these conditions, there are various attempts to develop a novel material for a sensor and a gas sensor.
Examples of gas sensors using ceramic include a semiconductor gas sensor, a solid electrolyte gas sensor, and a catalytic combustible gas sensor, which are distinguished by type, structure and material. An environmental gas sensor having characteristic that when an oxide semiconductor ceramic such as zinc oxide (ZnO), tin oxide (SnO2), tungsten oxide (WO3), titanium oxide (TiO2), or indium oxide (In2O3) is in contact with an environmental gas such as H2, CO, O2, CO2, NOx, a toxic gas, a volatile organic gas, ammonia, or moisture, electrical resistivity is changed due to gas adsorption and oxidation/reduction, which occur at a surface of a metal oxide, has been widely researched. Such an environmental gas sensor is used as a commercially-available gas sensor.
Recently, much research on developing a gas sensor using an oxide semiconductor having a nano structure such as a nano thin film, nanoparticle, nanowire, nanofiber, nanotube, nanopore, or nanobelt, which has different characteristics from a bulk material has been progressing. A small size, particularly, a high surface-to-volume ratio, of this nano structure material enables manufacture of a sensor having fast response speed and high sensitivity. Such a novel material enables development of a gas sensor having excellent characteristics such as fast response speed, high sensitivity, high selectivity, and low power consumption.
However, a gas sensor using an oxide having a nano structure such as zinc oxide (ZnO), tin oxide (SnO2), tungsten oxide (WO3), titanium oxide (TiO2), or indium oxide (In2O3) is designed to sense a single gas, and thus cannot detect various environmental gases at the same time. To detect various environmental gases, a sensor formed in an array structure is needed.
Thus, a new approach to novel sensor materials, structures and processes is needed to develop a gas sensor compensating disadvantages of the conventional gas sensor formed of an oxide semiconductor and having excellent characteristics such as high sensitivity, high selectivity, fast response speed and long-term stability. To this end, today, the development of an oxide semiconductor nanofiber and a method of preparing the same, and a gas sensor using the same is actively progressing.
As a result, the present inventors found that by using a sensing layer in which different kinds of nanofibers are arranged, two kinds of gases can be sensed at the same time during development of an environmental gas sensor having high sensitivity, fast response, high selectivity, and long-term stability using a characteristic high specific surface area of a nanofiber, and thus completed the present invention.